If you fix a 3N load at a point 12 cm from the fulcrum, then at what distance should a 4N

If you fix a 3N load at a point 12 cm from the fulcrum, then at what distance should a 4N load be fastened to balance the lever?

F1 = 3 N.

r1 = 12 cm = 0.12 m.

F2 = 4 N.

r2 -?

The equilibrium condition for the lever is the equality of the moments of forces from opposite sides: M1 = M2.

The moment of force M is the product of the force F by the smallest distance from the line of action of the force to the axis of equilibrium r, which is called the shoulder: M = F * r.

M1 = F1 * r1.

M2 = F2 * r2.

F1 * r1 = F2 * r2.

r2 = F1 * r1 / F2.

r2 = 3 N * 0.12 m / 4 N = 0.09 m.

Answer: in order to balance the lever, the second weight must be attached at a distance r2 = 0.09 m from the balance axis.